Headroom, it's threaded so you might be able to straighten the sights by tightening a little but be careful. Before you do anything to that rifle you might look a little into it's value. There were very few made that were marked Mod.40. It became the 27S shortly after they began production. I'd contact the Marlin Collector's Assoc at 407 Lincoln Bldg, 44 Main St., Champaign, IL 61820. George